The invention relates to a filter element, particularly for filtering the intake air of an internal combustion engine, which is constructed to minimize the pressure drop across the filter.
U.S. Pat. No. 6,312,489 (=DE 198 16 431), for example, discloses a filter element in which the folded filter insert has a contour on one side that at least partially deviates from a plane in two dimensions and is zig-zag folded or pleated throughout. According to the description of this published application, the filter element may be readily adapted or fitted to complex structures in the intake area of an internal combustion engine to optimize the filtering effect through better use of the space in the area on the intake side of the filter insert. Because the filter element is well seated against the structural configuration of the intake tract, the described filter element also improves the flow behavior on the air inlet side of the filter element.
U.S. Pat. No. 5,391,212 (=DE 42 18 396) discloses the production of filter elements, particularly for use in internal combustion engines of trucks and construction machinery, with a relatively large filter surface. These filter elements have a seal on one side, which extends at least along the rim so as to achieve a tight seal between the unfiltered air side and the filtered air side of the filter element.
These prior-art filter elements may be configured to take into account specific geometries in the filter housing or on the adjacent units by connecting together separate filter elements whose folds have different heights. The individual filter elements are manufactured separately and are interconnected by additional connecting webs, which also act as hinges.